Birds and All Nature, Vol. 5, No. 1, January 1899 / Illustrated by Color Photography

by Various

These papillæ have within them capillary blood vessels and the filaments of nerves. They are the seat of the tongue's sensibility. Whatever is tasted must come into chemical action over these little points. Moderate pressure helps the sensation, so we smack our tongues sometimes when we are not in company. Cold deadens taste to some extent and heat acts in nearly the same way. Rinse the mouth with very warm or very cold water and then take in a solution of quinine at about forty degrees temperature and the bitter fluid will have almost no bitterness till the temperature of the mouth and its contents becomes somewhere near one hundred degrees.

Three things are necessary in a substance in order that it may be tasted, and it is curious to note how common are all three. First, it must be easily mixed with the saliva; second, it must easily spread itself about so that it may mingle with the mucus that always covers the papillæ; and third, it must be capable of acting chemically on the protoplasm of the end organs when once it gets into the taste bulb. All tasteless substances have one or more of these qualities lacking. Wipe the tongue dry and place a sugar crystal upon it. No taste will be experienced until the spot is moistened.

All substances do not taste alike to different tongues. We have noted the difference in appreciation of certain foods in infancy and in mature years. Water tastes differently to the fever patient and to the well man. As substances taste differently at different times to the same person, so they vary with individuals. One tongue is found on careful examination to have three times as many papillæ as another, one system is more susceptible to chemical action than another, and the nervous system varies enough in different subjects to make a considerable difference in the powers of taste.

One guest at table is delighted with a dish which appeals not at all to the palate of his neighbor. In fact there are cases where the power of taste has been temporarily or entirely lost. In such cases the patient goes on with his daily eating in a mechanical way, not because it tastes good, but because he must.

There seem to be different nerves for sweet, for bitter, for salty things, and for acids. Substances are known to chemistry which act differently on the nerves of the front and those of the back of the tongue. They very curiously taste sweet to the nerves of the tip of the tongue and at the same instant bitter to those at the base. If leaves of the Gymnema sylvestre be chewed, sweet and bitter things are tasteless for awhile although acids and salts are tasted as usual.

Let an electric current pass through the tongue from the tip to the root and a sour taste will be experienced at the tip. But no one has yet explained why when the same sort of current is passed through in the opposite direction the taste is alkaline.

Place a small piece of zinc under the tongue and a dime on top. The saliva which moistens them will cause them to form a small galvanic battery. As they are allowed to touch each other at the tip of the tongue a sour taste will be experienced and in the dark a spark will appear to the eyes.

There is a pretty microscopic formation on the sides of some of the papillæ. It consists of rows of small openings or sacs egg-shaped with very minute mouths at the surface. These are known to science as taste bulbs. They are so small that three hundred of them put together the long way will scarcely reach one inch. They are so numerous that 1,760 have been counted on one papilla of an ox's tongue. They are not entirely confined to the surface of the tongue, for they have been found in large numbers upon the soft palate and the uvula, and many have been discovered on the back side of the throat and down into the voice box, some of them even appearing upon the vocal cords. Their form is much like that of a long musk melon, but they are too small to be seen by the naked eye. The outer part or rind consists of rows of cells evidently formed to hold what is within. On the inside are from five to ten taste cells which are long enough to reach the whole length of the bulb and protrude slightly at the opening where they are finely pointed. They are attached at the other end and branch out as if to run to several extremely fine divisions of the nerves.

Birds and reptiles have no taste bulbs in their papillæ. Tadpoles and freshwater fishes have similar bulbs in their skin, and it is thought they enjoy the taste of things around them without the necessity of taking them in at the mouth.

We give the sense of taste more credit sometimes than it merits. What we regard as tastes are often flavors or only smells. What is taken in at the mouth gets to the nose by the back way if it is of the nature of most spices, and so by use of the nose and the imagination we taste things that do not affect the tongue at all. A cold in the head shows us we do not taste cinnamon, we merely experience its pungency as it smarts the tongue while its flavor we enjoy only with the nose.